The present invention relates to a channel selecting device suitable for use particularly in a transceiver or the like.
When channel selection is performed by a channel selector as in the case of a transceiver, a rotary switch has usually been employed which is provided with one sliding contact and fixed contacts the number of which corresponds to that of channels. In this case, a limit is inevitably imposed on the number of channels or that of the fixed contacts, since the fixed contacts must be arranged about an axis in a circular form on a base board limited in size. When the required number of channels exceeds this limit, a plurality of switching units sufficient for meeting the required number of channels must be coaxially arranged with one on top of the other resulting in an increase of the occupied space. Moreover, in such an arrangement, contact switching is made by the rotation of a common axis and, therefore, selection of a desired channel from among the channel block of each switching unit requires discrimination of signals for clockwise and counterclockwise rotations, i.e., the increase and decrease of the channel number, resulting in an increase of complexity. In addition, the rotary type switching is inherently low in response speed.
As mentioned above, a transceiver or the like is usually so made that channel selection may be performed by operating a channel selector and, for instance, that channel scanning performed with a press-to-talk button switch of a hand microphone or the like kept depressed may unlock a frequency synthesizer of phase-locked loop type installed therein to let the synthesizer perform abnormality-preventing functions thereby preventing the transmission of jamming waves. But, such an arrangement is not necessarily able to completely eliminate abnormalities such as the transmission of jamming waves. For this reason, the advent of a new channel selecting device is eagerly hoped for that can be easily attached to the scanner of an existing transceiver or the like and in addition can completely prevent the transmission of jamming waves.